I was in New York City a couple of weeks ago with my X-Pro1. I had great success using zone-focusing to shoot without looking while walking around. My basic methodology:

1) Switch to a mode that doesn't use the rear viewfinder to save battery

2) Setting my 18-55 to 18 and prefocusing on an object around maybe 4 feet away (basically whatever seemed to be a normal distance I would pass people on the sidewalk).

3) Set the camera to f/8 (and be there. Although a few times I then accidentally changed the aperture by bumping the lens), 1/125th or 1/250th (to freeze motion), and Auto ISO 6400 (let the camera pick the ISO to control the exposure).

4) Walk around with camera around my neck, steadying with my hand, with a finger on the shutter ready to snap if I saw something interesting.

In general, it worked very well for me. I certainly got more shots than if I'd tried to bring to the eye and frame a shot quickly. A few were out of focus or I'd really missed with the framing (although that was rare at 18m).

Here are a couple:

EDIT TO ADD: Don't know why DPReview makes these look so fuzzy. Click the original size to see it correctly.